Review Packet for Unit 5 Test
This test will cover all of Chapters 6 and 7, along with parts of Chapter 24
You should be familiar with the following concepts and facts:
Structure of Chromosome

Chromatids - The two exact copies that make up a chromosome

Centromere – The two chromatids of a chromosome are attached at a point
called the centromere.
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Gene – A segment of DNA that codes for a protein or RNA molecule
Diploid and Haploid number of chromosomes

How many chromosomes in human somatic cells? - 46

How many chromosomes in human sex cells? - 23
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What is a haploid cell? – A cell with one set of chromosomes – In animals,
gametes are haploid.

What is a diploid cell? – A cell with two sets of chromosomes. In animals,
somatic cells are diploid.
Autosomes and Sex Chromosomes

What is an autosome? - Chromosomes are not directly involved in determining
the sex (gender) of an individual.

What is a sex chromosome? Pair of genes that determine the sex of the
individual (XX for human females, XY for human males).

How many autosomes in somatic cells? In humans, 44.

How many sex chromosomes in somatic cells? In humans, 2.
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How many autosomes in gametes? In humans, 22.

How many sex chromosomes in gametes? 1

How is sex of offspring determined? By the male gamete – in humans, if the
sperm carries an X chromosome, then the fetus will be XX – female. If the
human sperm carries a Y chromosome, then the fetus will be XY – male.

What is a zygote? – A fertilized egg cell. The first cell of a new individual.

Is a zygote haploid or diploid? Diploid

How many sperm can fertilize one egg? One
What is trisomy?

What is trisomy 21? A Birth defect in humans also called “Down Syndrome”

How does trisomy occur? By a process called “non-disjunction”.

What is non-disjunction? When sperm and egg cells form, each chromosome
and its homologue separate. If one or more chromosomes fail to to separate
properly, one new gamete ends up with both chromosomes and the other
receives none.

What is a karyotype and why would we want to look at one? A photo of the
chromosomes in a dividing cells that shows the chromosomes arranged by size.
We would want to look at one to detect abnormalities in chromosome number
Mutations

What is a mutation? Changes in an organism’s chromosome structure.

Name and describe 4 types of chromosomal mutation - Deletion – a piece of
chromosome breaks off completely. Duplication – a chromosome fragment
attaches to its homologous chromosome. Inversion – a chromosome piece
reattaches to the original chromosome but in a reverse orientation.
Translocation – chromosome piece breaks off and reattaches to a nonhomologous chromosome.
Reproduction in Prokaryotes

Circular DNA duplication – prokaryotes (bacteria) have circular DNA. The
duplication of this chromosome is the first step in the process of asexual
reproduction.

Binary Fission – A form of asexual reproduction that produces identical
offspring.
Cell Cycle

In what stage does a cell spend most of its time? G1 of interphase

What are the stages in a somatic cell’s life-cycle? Know the order of the
stages (G1, S, G2, M, C). G1 (G1 - Growth 1 or Gap 1, S – Synthesis, G2 – Growth
2 or Gap 2, Mitosis, Cytokinesis)

When is DNA unwound during the cell cycle? During interphase

Why is DNA unwound during the cell cycle? So that other molecules in the cell
can access the genetic information stored in the DNA

What are the stages of Mitosis? Prophase, Metaphase, Anaphase, Telophase

What happens during the S phase? DNA replication

What happens during each phase of Mitosis? How does the cell look during
each phase? See pages 130-132 in your book

What is the result of Mitosis? 2 new cells which are genetically identical to
their parent cell and to each other

What is cancer? Uncontrolled cell growth.

When do the major checkpoints happen during the cell cycle and what do
they do? G1 Checkpoint – makes the decision whether the cell will divide. G2
Checkpoint – DNA replication is checked. Mitosis checkpoint – triggers exit
from mitosis

Describe the genetic information in the daughter cells produced by mitosis in
comparison with the genetic information in their parent cell. Genetic
information in daughter cells is same as that in the parent cell.
Formation of haploid sex cells

What is meiosis? – Form of cell division that halves the number of
chromosomes when forming specialized reproductive cells such as gametes (in
animals) or spores (in plants).

What are the mechanisms during meiosis that lead to new genetic
combinations? Crossing over, independent assortment and random
fertilization.

What is crossing over and when does it happen? Portions of the chromatid on
one homologous chromosome are broken and exchanged with the
corresponding chromatid portions of the other homologous chromosome. This
happens during Prophase I of Meiosis.

What is independent assortment and when does it happen? Random
distribution of homologous chromosomes during meiosis. This happens during
Metaphase I of Meiosis.

What is meant by “random fertilization”? Zygote that forms during
fertilization is created by the random joining of two gametes which are
produced independently. Number of possible fertilizations is 64 trillion.

Why is genetic recombination important? It is essential to evolution. It
generates genetic variation quickly. Pace of evolution appears to increase as
the level of genetic variation increases.

What would happen if meiosis didn’t occur and gametes had a diploid
number of chromosomes? Be prepared to write an essay question on this
topic. Each generation would have twice as much genetic material as the
previous one . The amount of genetic material held in the nuclei of the cells of
each subsequent generation would increase exponentially. This would not be
feasible in terms of the sheer amount of DNA in the cell – it would also lead to
structural and developmental problems with the offspring.

Why is genetic variation in a population important? Be prepared to write an
essay question on this topic. The pace of evolution speeds up as a result of
genetic recombination. In the face of adverse environmental circumstances or
disease, a population is more likely to have members that survive if there is
diversity in the genetic makeup of the individuals making up the population.

What is the name of the male gamete in animals? sperm

What is the name of the female gamete in animals? Eggs or ova

Describe the genetic information in the daughter cells produced by meiosis in
comparison with the genetic information in their parent cell. Daughter cells
have half the genetic material as the parent cell. Each daughter cell will be
genetically different from each of its sister cells.

What is a polar body? Cytokinesis during oogenesis (production of egg cells by
meiosis) results in the an uneven distribution of cytoplasm. On of the resulting
cells gets nearly all of the cytoplasm. This cell will become the egg cell. The
other cells, without enough cytoplasm, are called “polar bodies”. They do not
survive.

How many gametes are produced by spermatogenesis? 4. See page148 of
textbook.

How many ova are produced by oogenesis? 1. See page 148-149 of textbook.
Sexual and Asexual Reproduction

Compare and contrast sexual and asexual reproduction. Asexual
reproduction involves one parent that produces offspring which are
genetically identical to the parent. Sexual reproduction involves two parents.
They produce reproductive cells (gametes) that fuse to form a new organism.
The offspring is genetically different from either parent.

What are some benefits of asexual reproduction? Simple. Produces many
offspring in a short period of time. No need to spend time or energy producing
gametes or looking for mate.

What are some drawbacks of asexual reproduction? Lack of genetic diversity
in offspring.

What kind of genetic diversity will you find in a population of organisms
produced by asexual reproduction? They will all be the same (apart from
differences produced by occasional random mutation).

What are some benefits of sexual reproduction? Production of genetically
diverse offspring. New genetic combinations produced.

What are some drawbacks of sexual reproduction? Time and energy spent
producing gametes and finding mates.

What kind of genetic diversity will you find in a population of organisms
produced by sexual reproduction? It will be much more diverse than a
population produced from asexual reproduction.
Plant Cells

Compare and contrast cytokinesis in plants and animals. In plant cells,
cytoplasm is divided in a different way than in animals. In plant cells, a cell
plate is produced half-way between the two new nuclei produced by mitosis.
New cell walls then form on each side of the cell plate. When complete, the cells
plate separates the plant cell into two new plant cells.

Be able to label the parts of a flower on a diagram. See page 538 of textbook.

Be able to describe the function of the various parts of a flower. See page 538
of textbook.

Why do plants produce colorful, sweet-smelling flowers? To attract animals
that act as pollinators for the plant.

What is pollen? Where is it produced? Immature male gametophyte of a seed
plant produced by the male sexual organs of a flower.

What is an anther? A part of a flower – a pollen-producing sac.

What is a stamen? Male portion of flower – consists of filament and anther.

What is a pistil? Female portion of flower – consisits of ovary, style and stigma.

What is a style? Tube-like structure of stamen that holds up stigma.

What is an ovary? Part of flower that contains the ovules. A swollen structure
at the base of the pistil.

Where are eggs produced? In the ovule.

What is a sporophyte? Diploid part of a plant’s lifecyle that produces haploid
unicellular spores.

What is a gametophyte? Multicellular haploid part of a plant’s lifecyclet that
produces haploid gametes.

In seed plants, what do male gametophytes produce? sperm

In seed plants, what do female gametophytes produce? Egg or ovum

What is a seed? Structures that contain the embryos of seed plants. It forms
from the ovule of a flower after the egg within it has been fertilized.

Describe the structure of a seed. See page 535 of your textbook.

What is the purpose of the seed coat? Protects embryo from injury and harsh
environment.

What is a cotyledon? What purpose does it serve in the developing plant?
Starchy part of seed attached to embryo – they transfer nutrients to developing
embryo.

Distinguish between monocots and dicots in terms of the number of
cotyledons found in their seeds. Monocots have one cotyledon. Dicots have
two cotyledons.

What is the name of the partially developed plant found in a seed? Embryo.